1. Field of Invention
The present invention relates to an antenna apparatus. More particularly, the present invention relates to a miniature monopole antenna apparatus built in a wireless communication system.
2. Description of Related Art
According to the progress of communication technology, the key development is the transfer from wired to wireless communication, such as the popularization of wireless household phones and mobile phones. In the field of wireless communication, the signal carrier is invisible air waves, where the bridge between the electrical signal and the air waves is an antenna. That is to say, an antenna is certainly needed by a wireless communication device to transmit or receive air waves. An antenna is therefore an essential component in a wireless communication device.
In the conventional wireless communication device, the antenna apparatus is usually attached to the exterior of the device, and causes a variety of problems. For example, an antenna is easily damaged by external force, and the overhead of the circuit design is rising and hard to carry. In addition, in accordance with the present design trend, many functions are integrated into a device, such as a mobile phone with the data processing function of a personal digital assistant (PDA) or a portable computer system with Bluetooth communicating function and wireless local area network (WLAN). Thus, the amount of components and antennas will substantially increase in the device, but the volume of the device must be maintained within a range. For these reason, the external antenna is increasingly unsuited to use in advanced wireless communication devices.
Ii is apparent that the miniature antenna built in the wireless communication devices will be a mainstream trend in the communications field. The conventional built-in miniature antenna techniques comprise chip antenna and planer antenna, and have some problems. For example, a chip antenna connects with a communication system via a carrier, and the relations between the dielectric constant of the carrier and the operation frequency of the antenna, and between the dielectric constant of the carrier and the performance of the antenna, all are an inverse proportion. That is to say, if the chip antenna needs a lower operation frequency, the dielectric constant of the carrier must be higher, and causes a lower performance of the chip antenna. Besides, the mounting technique used by some of built-in miniature antennas may be different from the mounting techniques used by the communication system. Thus, the antenna and the system are difficult to integrate and expensive.